Human began to explore universe long long time ago,but we still know little about whole universe.We just know that it is enormous and there are countless planet flow in it.Whereas,thanks to astronomesr' tireless efforts,now we have a comprehensive knowledge about solar system that our earth earth belongs.
We know that every planet spining around their respective axis.For instance ,the earth rotates once every one day and one night, and the moon rotates once every lunar month.At the same time ,the moon do spinning motion around the earth,meanwhile the earth spinning around the sun. The solar system is like a huge complex machine i think .But it is just a drop in the bucket if compared with The Galaxy.We still don't know the size of the universe till now.Of course ,not this problem only ,we still have no idea about other broblem such as if there are life on other planet.With the development of technology, we could probably find the answer.
绝对原创,仅供参考!欢迎各种纠错,指正!